A catalytic structure for treating exhaust gases is provided which is obtained by spraying molten aluminum onto the surface of a substrate such as wire netting, expanded metal, etc. in the presence of oxygen, to form on said surface of a substrate a roughened surface through deposit of fine aluminum particles thereon and also an aluminum oxide layer on said roughened surface, and adhering onto this layer a catalytic substance such as a catalyst for reducing nitrogen oxides.The catalytic structure has a high catalyst-retainability to prevent the catalyst from readily peeling off from the surface even when a mechanical impact is applied thereto. Further it exhibits a superior corrosion resistance even in a corrosive environment containing sulfuric acid; hence it is suitably employed for the apparatuses for treating exhaust gases containing nitrogen oxides and sulfur oxides.